Over the past few years it has become the practice in the retail sales industry to utilize what is known in the packaging industry as "point of sales" packaging for the majority of products offered for sale. As would be expected, this practice has forced the packaging industry to develop and implement new equipment and operating practices, which would provide significant improvement in the quality of printing. In other words, the former "brown box" would no longer be acceptable.
Consequently, flexographic printing was introduced into the package printing industry and is now in widespread use. See, for example, an article published in the December, 1979, issue of Boxboard Containers, titled "It's Time For A Change In Flexo". As discussed in this article, flexographic printing entered this area of use in the 1960's when convertors begin installing the equipment necessary to initiate use of the flexographic printing process. The convertors could now print, slot, fold, glue, die-cut and bundle in a true production line manner with this new flexographic equipment.
In addition to all the advantages of the in-line operations, this change in equipment for flexography also offered the potential for extended capabilities and other improvements in package printing. However, those additional benefits were not immediately taken advantage of. For example, even with this new process and equipment, the convertors continued to use the same printing plate systems used prior to the introduction of the flexographic printing system. The printing plate system consisted of a rather thick rubber plate secured to a fabric which in turn was secured to a carrier material.
A significant change in the printing plate system used, occurred in the late 1970's and early 1980's when the Rogers Corporation introduced the use of a cellular polyurethane material as a backing for flexible printing plates. In this system, the flexible printing plates are secured directly to the polyurethane material which, in turn, is glued to the printing plate cylinder using either an adhesive film or "sticky back" tape. In some cases, the polyurethane material is adhered to and supported on a polyester backing material. In either case, the printing plate is secured directly to the upper surface of such polyurethane material.
Because the printing plate system is essentially glued on the working surface of the printing plate cylinder great care must be exercised in mounting such printing plate system to such working surface to ensure proper alignment.
It is also known in the prior art to use a substantially T-shaped member to align and secure one end of a printing plate composite to a bar-like member disposed on such working surface of the printing plate cylinder and substantially parallel to the longitudinal axis thereof. In this case, the printing plate is disposed on a vinyl-like sheet, which in turn, is engaged with the working surface of the printing plate cylinder. The T-shaped member is secured to one end of the sheet and the axially opposed other end of the sheet is secured to the printing plate cylinder with tape or strap-like members. This fastening system for the printing plate is commonly known in the industry as the Matthews Fast-Loc. Use of this system results in less downtime of the press being required to achieve proper alignment of the printing plate on the working surface of the printing plate cylinder.
Although each of the above-discussed improved printing plate systems have greatly advanced the printing of substrate materials used in the packaging industry, they also each have certain limitations in their use. For example, the Roger's printing plate system requires a considerable amount of time to set up in the press even though it enables poorer quality substrate material to be used and is not as sensitive to slight imperfections, which may be present, in the working surface of the printing plate cylinder. On the other hand, the Matthews Fast-Loc printing plate system can be set up very quickly on the press, although it requires higher quality substrate material and fewer imperfections in the working surface of such printing plate cylinder.